1. Field of the Invention
The instant invention relates to wear indicators for clutches. More particularly, the instant invention relates to wear indicators for monitoring the position of an adjusting ring in an adjustable clutch.
2. Background Art
In order to transmit drive from an engine-driven flywheel to an output shaft, many clutches utilize levers for selectively urging driving and driven discs into contact with one another. The levers have first ends pivoted on a release sleeve and second ends pivoted on a clutch cover which rotates with the flywheel. Intermediate the ends of each lever are abutment surfaces, which urge a pressure plate against the discs to effect frictional coupling of the discs. As the discs wear, the clutch will begin to slip if the position of the levers is not adjusted to compensate for the wear.
The adjustment is accomplished by an adjusting ring having an external thread which is threadably coupled to an internal thread of the clutch cover. By rotating the adjusting ring so as to axially advance with respect to the clutch cover and the drive train, the second ends of the levers may be advanced so as to maintain proper pressure between the abutting surfaces of the levers and the pressure plate.
Since the adjusting ring is positioned within the clutch cover, it is difficult to determine the amount of wear by external inspection of the clutch. Currently, with clutches utilizing adjusting rings, it is necessary to rely on scales and other measuring devices to accurately determine the position of the adjusting ring. This requires one to remove the clutch assembly from the vehicle, a time-consuming and somewhat expensive undertaking.
While the patent literature has recognized the advantages of monitoring clutch wear by observing an external indicator, such as a biased, sliding pin, a satisfactory approach for monitoring the position of an adjusting ring has not been addressed. When a clutch is equipped with an adjusting ring, the position of the adjusting ring indicates previous wear rather than current wear. The mechanic is thus presented with a choice between replacing the clutch (or, perhaps, the clutch components) or of simply modifying the position of the adjusting ring. If the adjusting ring has previously been adjusted to its fullest extent, the mechanic cannot perform adjustments on the adjusting ring so as to revive operation of the clutch. With the adjustable clutches currently in use, it is not readily apparent that a clutch needs to be pulled rather than adjusted by simply looking at the clutch housing.
In addition to having no indication of the adjusting ring, the clutches currently available with adjusting rings have no external indicator of how much an adjusting ring is being advanced by an adjustment. In other words, when the adjusting pinion which drives the adjusting ring is rotated, there is no indication of how much the adjusting ring moves axially as the pinion is turned. Of course, one can calculate how far the adjusting ring has moved axially by counting the number of rotations of the pinion, but this requires the mechanic to acquire and apply abstract knowledge and skill which, even if mastered still poses considerable risk of error since, once the adjusting pinion is rotated to advance the adjusting ring and then rotated to retract the adjusting ring, the mechanic can easily lose track of its actual position.